1. Field of the Invention
The present invention relates to a method for repairing a pattern defect caused on an electronic circuit board, the method being preferable for repairing a pattern defect caused on an electronic circuit formed on a thin film transistor substrate of a liquid crystal display device or an organic EL display device.
2. Description of the Related Art
With expansion of the liquid crystal display device market, demand for a lower price is growing and stricter. Meanwhile, a glass substrate for use in manufacturing of this kind of display device becomes larger every year, which makes it no longer possible to manufacture a liquid crystal display having an electronic circuit free from pattern defects only through process improvement. This is one of the major contributions of cost increase. In view of the above, a step of repairing such a pattern defect on an electronic circuit is indispensable in a manufacturing process. Here, note that a pattern defect on an electronic circuit includes not only a defect on a wiring or an electrode mounted on a thin film transistor substrate but also a defect on a general structural pattern, such as a semiconductor layer, an insulating layer, and so forth, of an electronic circuit. A defect on a black matrix layer and a color filter layer formed on a color filter substrate are also included.
A liquid crystal display device has a structure in which liquid crystal is sandwiched between a substrate (a thin film transistor substrate, a TFT substrate) where a thin film transistor (TFT) circuit is formed for each pixel and a color filter substrate (a CF substrate) where red, blue, green resin filters are arranged in a matrix. In this structure, if a pattern defect should be caused on a wiring, an electrode, or an insulating layer of a pixel circuit formed on the TFT substrate or a color filter on a color filter substrate, abnormal displaying is resulted, and the relevant liquid crystal display device is accordingly regarded defective. Abnormal displaying includes, e.g., color defect due to a resin film expanding to an adjacent pixel on a color filter, inconsistent application due to inconsistent thickness of a resin film, a pinhole, that is, a kind of inconsistent application of an orientation film for liquid crystal orientation, short circuit and/or disconnection of a wiring and/or an electrode forming a pixel circuit, and so forth.
As a technique for repairing such disconnection of an electronic circuit, Japanese Patent Laid-open Publication No. Sho 57-118246 discloses a method for repairing disconnection of a circuit by applying repairing material which will deposit low resistive metal through laser beam irradiation via, e.g., a micro syringe. Also, though not for pattern defect repairing, Japanese Patent Laid-open Publication No. 2004-45069 discloses a method, employed for an ink-jet application method, for addressing application instability due to dried application material (or ink) at a nozzle ejection hole. According to this method, a waste ejection position is provided outside a stage for transporting an application target, and application material is ejected for waste so that application is carried out after an application amount, or an ejection amount, to be ejected from a nozzle is stabilized.
In ink-jet defect repairing in a process of manufacturing, e.g., a TFT substrate of a liquid crystal panel, however, a problem may be caused with an application target TFT substrate larger than 2 m×2 m, despite provision of a waste ejection position outside an application target substrate, as described in the above mentioned Japanese Patent Laid-open Publication No. 2004-45069, such that the state, e.g., viscosity, of the repairing material (application material) at the tip end of the nozzle may be changed while the nozzle moves to a disconnected portion to be repaired, which hinders normal application of the application material. Further, quick-dry nature of repairing material to be applied may cause a problem such that the repairing material is dried while the nozzle moves from the waste ejection position to an application position, which also hinders normal stable application of the application material.
An object of the present invention is to provide a method for repairing a pattern defect caused on an electronic circuit board of a TFT substrate or a color filter substrate by applying liquid in a stable manner by preventing the tip end of a nozzle of an ink jet application apparatus from being dried while the nozzle moves from a waste ejection position to an application position due to quick-dry nature of liquid application material or the large size of an application target.